This invention relates to an electrostatographic printing machine, and more particularly concerns an apparatus for permanently affixing heat settable particles to a sheet.
In a typical electrostatographic printing machine, a latent image recorded on a surface is developed with heat settable charged particles. The particles are transferred to the sheet in image configuration. Thereafter, the particles are permanently affixed to the sheet forming a permanent copy of the original document. Both electrophotographic and electrographic printing are types of electrostatographic printing. Electrophotographic printing charges a photoconductive member to a substantially uniform level. A light image of an original document irradiates a charged photoconductive member to dissipate the charge to record thereon an electrostatic latent image. Electrographic printing does not employ a photoconductive member, nor a light image of the original document to create a latent image. However, both of these processes generally employ heat settable particles. The particles are permanently affixed to the sheet of support material by the application of heat thereto. Hereinafter, electrophotographic printing will be discussed as an exemplary printing process employing the features of the present invention therein.
Various techniques have been devised for applying heat to the particles transferred to the sheet of support material. One approach passes the sheet of support material through a radiant oven which applies sufficient heat to permanently fuse the toner particles to the sheet. An alternate approach utilizes rollers through which the sheet of support material passes. One or both of these rollers may be heated.
In fusing systems of the foregoing type, it is highly desirable to control the temperature. Various prior art devices have been developed to measure the temperature of the fuser roll. Exemplary of these is U.S. Pat. No. 3,690,176 issued in 1972 to Connolly et al.. As described therein, a thermistor, mounted pivotably about two axes, contacts a heated fuser roll.
Accordingly, it is the primary object of the present invention to improve temperature sensing of heated roll fusers.